<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - WebXR - Look to Select w/cursor</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import { VRButton } from 'three/addons/webxr/VRButton.js';

function main() {

	const canvas = document.querySelector( '#c' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );
	renderer.xr.enabled = true;
	document.body.appendChild( VRButton.createButton( renderer ) );

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 0.1;
	const far = 50;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.set( 0, 1.6, 0 );

	const scene = new THREE.Scene();
	{

		const loader = new THREE.CubeTextureLoader();
		const texture = loader.load( [
			'resources/images/grid-1024.png',
			'resources/images/grid-1024.png',
			'resources/images/grid-1024.png',
			'resources/images/grid-1024.png',
			'resources/images/grid-1024.png',
			'resources/images/grid-1024.png',
		] );
		scene.background = texture;

	}

	{

		const color = 0xFFFFFF;
		const intensity = 3;
		const light = new THREE.DirectionalLight( color, intensity );
		light.position.set( - 1, 2, 4 );
		scene.add( light );

	}

	function makeDataTexture( data, width, height ) {

		const texture = new THREE.DataTexture( data, width, height, THREE.RGBAFormat );
		texture.minFilter = THREE.NearestFilter;
		texture.magFilter = THREE.NearestFilter;
		texture.needsUpdate = true;
		return texture;

	}

	const boxWidth = 1;
	const boxHeight = 1;
	const boxDepth = 1;
	const boxGeometry = new THREE.BoxGeometry( boxWidth, boxHeight, boxDepth );

	const sphereRadius = 0.5;
	const sphereGeometry = new THREE.SphereGeometry( sphereRadius );

	function makeInstance( geometry, color, x ) {

		const material = new THREE.MeshPhongMaterial( { color } );

		const cube = new THREE.Mesh( geometry, material );
		scene.add( cube );

		cube.position.x = x;
		cube.position.y = 1.6;
		cube.position.z = - 2;

		return cube;

	}

	const meshToMeshMap = new Map();
	[
		{ x: 0, boxColor: 0x44aa88, sphereColor: 0xFF4444, },
		{ x: 2, boxColor: 0x8844aa, sphereColor: 0x44FF44, },
		{ x: - 2, boxColor: 0xaa8844, sphereColor: 0x4444FF, },
	].forEach( ( info ) => {

		const { x, boxColor, sphereColor } = info;
		const sphere = makeInstance( sphereGeometry, sphereColor, x );
		const box = makeInstance( boxGeometry, boxColor, x );
		// hide the sphere
		sphere.visible = false;
		// map the sphere to the box
		meshToMeshMap.set( box, sphere );
		// map the box to the sphere
		meshToMeshMap.set( sphere, box );

	} );

	class PickHelper {

		constructor( camera ) {

			this.raycaster = new THREE.Raycaster();
			this.pickedObject = null;
			this.pickedObjectSavedColor = 0;

			const cursorColors = new Uint8Array( [
				64, 64, 64, 64, // dark gray
				255, 255, 255, 255, // white
			] );
			this.cursorTexture = makeDataTexture( cursorColors, 2, 1 );

			const ringRadius = 0.4;
			const tubeRadius = 0.1;
			const tubeSegments = 4;
			const ringSegments = 64;
			const cursorGeometry = new THREE.TorusGeometry(
				ringRadius, tubeRadius, tubeSegments, ringSegments );

			const cursorMaterial = new THREE.MeshBasicMaterial( {
				color: 'white',
				map: this.cursorTexture,
				transparent: true,
				blending: THREE.CustomBlending,
				blendSrc: THREE.OneMinusDstColorFactor,
				blendDst: THREE.OneMinusSrcColorFactor,
			} );
			const cursor = new THREE.Mesh( cursorGeometry, cursorMaterial );
			camera.add( cursor );
			cursor.position.z = - 1;
			const scale = 0.05;
			cursor.scale.set( scale, scale, scale );
			this.cursor = cursor;

			this.selectTimer = 0;
			this.selectDuration = 2;
			this.lastTime = 0;

		}
		pick( normalizedPosition, scene, camera, time ) {

			const elapsedTime = time - this.lastTime;
			this.lastTime = time;

			const lastPickedObject = this.pickedObject;
			// restore the color if there is a picked object
			if ( this.pickedObject ) {

				this.pickedObject = undefined;

			}

			// cast a ray through the frustum
			this.raycaster.setFromCamera( normalizedPosition, camera );
			// get the list of objects the ray intersected
			const intersectedObjects = this.raycaster.intersectObjects( scene.children );
			if ( intersectedObjects.length ) {

				// pick the first object. It's the closest one
				this.pickedObject = intersectedObjects[ 0 ].object;

			}

			// show or hide cursor
			this.cursor.visible = this.pickedObject ? true : false;

			let selected = false;

			// if we're looking at the same object as before
			// increment time select timer
			if ( this.pickedObject && lastPickedObject === this.pickedObject ) {

				this.selectTimer += elapsedTime;
				if ( this.selectTimer >= this.selectDuration ) {

					this.selectTimer = 0;
					selected = true;

				}

			} else {

				this.selectTimer = 0;

			}

			// set cursor material to show the timer state
			const fromStart = 0;
			const fromEnd = this.selectDuration;
			const toStart = - 0.5;
			const toEnd = 0.5;
			this.cursorTexture.offset.x = THREE.MathUtils.mapLinear(
				this.selectTimer,
				fromStart, fromEnd,
				toStart, toEnd );

			return selected ? this.pickedObject : undefined;

		}

	}

	const pickHelper = new PickHelper( camera );
	scene.add( camera );

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	function render( time ) {

		time *= 0.001;

		if ( resizeRendererToDisplaySize( renderer ) ) {

			const canvas = renderer.domElement;
			camera.aspect = canvas.clientWidth / canvas.clientHeight;
			camera.updateProjectionMatrix();

		}

		let ndx = 0;
		for ( const mesh of meshToMeshMap.keys() ) {

			const speed = 1 + ndx * .1;
			const rot = time * speed;
			mesh.rotation.x = rot;
			mesh.rotation.y = rot;
			++ ndx;

		}

		// 0, 0 is the center of the view in normalized coordinates.
		const selectedObject = pickHelper.pick( { x: 0, y: 0 }, scene, camera, time );
		if ( selectedObject ) {

			selectedObject.visible = false;
			const partnerObject = meshToMeshMap.get( selectedObject );
			partnerObject.visible = true;

		}

		renderer.render( scene, camera );

	}

	renderer.setAnimationLoop( render );

}

main();
</script>
</html>
